The role of complementarity and facilitation in influencing tree community resilience

昆虫和病原体的非本地入侵以及气候变化等全球变化因素正在对世界许多地区许多树种的生长和生存以及许多森林生态系统的功能产生负面影响。目前的研究表明，树种混合可以更好地应对压力环境事件。然而，在什么类型的林分和环境条件下使用什么类型的混合物才能最大限度地提高森林对自然和人为压力源的恢复能力尚不清楚。在这个发现研究计划中，我打算测试关于森林组成和结构如何与基本共存机制相互作用的几个假设，以促进（或不促进）树木和森林对许多不同的永久和/或间歇性压力因素单独或联合作用的抵抗力和恢复（两种恢复力的衡量标准）。我将结合使用受控实地实验和在管理和非管理森林中设置的永久地块来调查这些问题。我将与研究生和博士后密切合作，并与世界各地的科学家合作回答这些问题。 目前正在加拿大魁北克省里彭附近建立一项雄心勃勃的新实地实验，以不同密度和空间布置种植各种树种的混合物，以在受控环境中测试其中一些假设。来自超过 25 个国际树木多样性实验的数据还将用于测试树木多样性如何影响森林在各种气候条件和树种混合物中应对各种压力的恢复力。我们将利用来自 60 多个国家的各种环境条件下的管理森林和天然林中建立的小型和大型永久土地来提高我们研究结果的实际相关性并测试我们研究结果的普遍性。将根据已知的近期发生的气候和生物应激源来研究树木和地块尺度的生长和死亡率。 这项研究的结果将用于设计新颖的管理方法，以提高面临全球变化的树木的恢复力和生存能力，从城市公园和花园、农作物、管理森林到大片林地保护区。随着我们面临管理和恢复日益新颖和紧张的生态系统的日益严峻的挑战，更好地了解维持或增加树木多样性和林分复杂性的好处开辟了许多可能的应用。

Global change factors such as non-native invasion of insects and pathogens as well as climate change are negatively affecting the growth and survival of many tree species and functioning of many forest ecosystems in a great number of regions in the world. Current studies indicate that mixtures of tree species can better cope with stressful environmental events. However, what types of mixtures to use under what types of stand and environmental conditions to maximise forest resilience to natural and human-induced stressors are mostly unknown. In this discovery research program, I intend to test several hypotheses regarding how forest composition and structure are interacting with basic coexistence mechanisms to promote (or not) both tree and forest resistance and recovery (both measures of resilience) to many different permanent and/or intermittent stressors acting alone or in conjunction. I will use a combination of controlled field experiments and permanent plots set in managed and unmanaged forests to investigate these questions. I will work closely with graduate students and Post-Docs and collaborate with scientists from around the world to answer these questions. An ambitious new field experiment where various mixtures of tree species grown in different densities and spatial arrangements is currently being established near Ripon in Quebec, Canada, to test some of these hypotheses in a controlled setting. Data from more than 25 international tree-diversity experiments will also be used to test how tree diversity affects forest resilience to various stressors in a wide set of climatic conditions and tree species mixtures. Small and large scale permanent plots established in managed and natural forests in a wide range of environmental conditions from more than 60 countries will be used to increase the practical relevance of our findings and to test the generality of our findings. The growth and mortality at the tree and plot scales will be studied in relation to known recent climatic and biotic stressors that have occurred. The results of this study will be used to design novel management approaches for increasing the resilience and survival of trees facing global change from urban parks and gardens, agricultural crops, and managed forests to vast protected areas of forested land. A better understanding of the benefits of maintaining or increasing tree diversity and stand complexity opens up many possible applications as we face the increasing challenge of managing and restoring increasingly novel and stressed ecosystems.